<!DOCTYPE>
<html>
<head>
<meta charset="utf-8">
<title>>CSS基本语法</title>
<style>

div{
    box-sizing:border-box;
    width:200px;
    height:100px;
    margin: 20px;
    border: 20px solid red;
    padding: 20px;
}
</style>
</head>
<body>
<div>this is a  div</div>
<p>this is a paragraph</p>
</body>


</html>

